The present invention relates to a material having a crystalline orientation film formed of titanium dioxide on a surface of a substrate such as a metal, a glass, a pottery, ceramics, plastics or the like. The material having the titanium dioxide crystalline orientation film is excellent in properties such as an antimicrobial activity, a stain resistance, an ultra-hydrophilic property and the like, and is widely used as kitchen appliances such as cooking utensils, tableware and a refrigerator, tools for medical care, materials for a toilet or a toilet room, a filter of an air-conditioner, electronic parts, building materials and road-associated materials.
It has been so far known that a titanium dioxide thin film exhibits various functions through a photocatalytic reaction. It has been also known that the titanium dioxide thin film is formed on a surface of a substrate such as a metallic material, a semiconductor element, a plastic material or the like and is used as an antireflection material, a sensor material, an insulating material or the like. Further, as a method for forming a titanium dioxide thin film on the surface of such a substrate, a coating method, a dipping method, a sputtering method and a CVD method in which a metallic heat-evaporated vapor is introduced into an oxygen gas atmosphere for reaction have been known.
Of these conventional methods for forming a titanium dioxide thin film, the coating method and the dipping method cannot form a titanium dioxide crystalline orientation film, and the sputtering method can hardly control the crystal structure of the thin film obtained. In the conventional CVD method, in order to form a crystalline titanium oxide thin film on a surface of a substrate, it was required that a substrate is usually heated at a high temperature of from 500 to 800xc2x0 C. and the formation of the thin film is conducted under reduced pressure in a closed plating chamber. In this conventional CVD method, the deposition rate of the titanium dioxide thin film was quite low, and the crystal structure of the thin film obtained was hardly controlled, making it impossible to obtain a crystalline orientation film oriented in a specific direction.
It is therefore an object of the present invention to provide a material having a titanium dioxide crystalline orientation film oriented in a specific direction on a surface of a substrate.
A further object of the present invention is to provide a method for preparing a material having a titanium dioxide crystalline orientation film oriented in a specific direction on a surface of a substrate efficiently at a low temperature.
The present inventors have found that the resulting titanium dioxide crystalline orientation film oriented in the specific direction is excellent in properties such as an antimicrobial activity, a stain resistance, an ultra-hydrophilic property and the like.
The material having the titanium dioxide crystalline orientation film on the surface of the substrate in the present invention is characterized in that the crystalline orientation film is oriented in the direction selected from crystal faces (001), (100), (211), (101) and (110) at right angles to the crystal surface. Thus, the excellent properties such as the outstanding antimicrobial property, stain resistance and the like can be provided for the first time by forming the titanium dioxide crystalline orientation film oriented in the above-mentioned specific direction on the surface of the substrate. Examples of the substrate include a metal, a glass, a pottery, ceramics, plastics, and a product having a film formed through plating with silver, chromium and the like on the surface of the above-mentioned substrate.
The titanium dioxide crystalline orientation film of the present invention refers to an orientation film formed of titanium dioxide single crystals or an orientation film formed of titanium oxide polycrystals. The single crystalline orientation film here referred to includes, as ordinarily used in the field of materials, not only one composed of single crystals but also one composed of plural crystals of which the three-dimensional crystal directions are consistent.
The material having the titanium dioxide crystalline orientation film which is oriented in the specific direction in the present invention can be produced for the first time by spraying a vaporized titanium alkoxide (starting complex) onto a surface of a substrate heated under atmospheric pressure along with an inert gas as a carrier.